"And tell me again, my good man," a disembodied, emotionless voice asked, "exactly what kind of machine was it that you called me?"

"A computer."

"A computer. An odd name, that. An analysis of its structure, assuming that the word reflects a traditional etymology, leads one to speculate that this particular device is able to perform certain types of mathematical calculations, which it then extrapolates into numerical values. Am I correct?"

"Only partially, sir. Well, no. Forgive me. Now that I think about it, your description is unerringly accurate. Strictly speaking, that's exactly what a computer does. However, the manner in which it can manipulate and apply the results of any operations it performs elevates a computer far above the status of a mere calculator."

"I would hope so. Your revelation that I am more machine than man is disturbing enough without placing further restrictions on my capabilities. Rare would be the individual who could anticipate discovering that his entire existence has been... Has been what? I suppose the only way to state it would be to call the life I once thought I led an illusion.

"And yet, here I am, living proof -- if this is itself not an illusory turn of a phrase -- that such incredible events can, indeed, occur. Where I once believed myself to be human, the very pinnacle of evolution's handiwork, I now find that I am, and ever have been, a mere machine, some mysterious device which you call a computer."

"Actually, sir, that's not quite correct, either. To be more precise, you're what's referred to as a computer program -- a series of coded instructions that, when executed by a computer, allow it to accomplish a specific task."

"Hmmm. All of this is beginning to sound quite complicated." In my mind's eye, I could almost visualize him (for I still thought of Holmes as a him, having no desire to relegate the famed detective to it status) drawing upon his familiar pipe, sifting through the information now in his possession, contemplating its significance. "And just what was the designated purpose of the particular computer program that you claim defines my being?"

"Stated simply, you were, um, created to assist in the collection, collation and analysis of evidence associated with selected criminal investigations. That's an undertaking, I might add, for which a well designed computer program is ideally suited. And as I implied earlier, sir, you are an amazing piece of work."

Several seconds of silence followed this observation. This time, I could conjure up no image of how Holmes might be reacting to my comments. How would I feel, I pondered, were someone suddenly to reveal to me that I was not the man I'd always believed myself to be? Indeed, that I was not a man at all!

To his credit, once Holmes assimilated this information, he responded with his customary poise and the insatiable curiosity that the legendary detective displayed throughout his long and illustrious (and, yes, he was correct, largely illusory) career.

"Well, there you have it, then. If what you say is true -- and ignoring for the moment the natural aversion any rational entity would feel toward the situation you describe, I see no reason to doubt your veracity -- the only practical course open to me is to accept the facts of my existence as you've outlined them and continue performing those tasks for which, apparently, I was, ah, constructed.

"It seems logical to postulate, therefore, that you have summoned me, however such a summoning might be accomplished, so that you might consult with me on matters relating to some criminal activity. So explain to me, my good man, the exact nature of the crime that has presumably confounded you. I trust the investigation of it shall prove worthy of my unique talents."

"Oh, it will, Mr. Holmes. I assure you, it will -- assuming, of course, that you're at all curious as to the recent activities of your most notorious antagonist, Professor Moriarty."

Holmes, that incredible piece of programming which I still tended to perceive from a decidedly human perspective, had a lot to catching up to do. The techniques and technology employed by both the criminal element and those charged with containing it had changed dramatically in the century since he was first created. I spent the greater part of two months upgrading him (it) to state-of-the-art status. My efforts produced some pretty impressive results, if I do say so myself.

When I opened the door the holographic Holmes had been leaning back in a virtual armchair, eyes only half open, fiddle thrown across his knee, carelessly scraping the bow across its strings. I must admit, I briefly considered eliminating this musical subroutine. It was pleasant enough when replicating identifiable passages. Like Watson had before me, I rather enjoyed Mendelssohn's Lieder and several other pieces it contained; on a whim, I even added a semi- Classical interpretation of Strawberry Fields Forever. The effect was quite the opposite, however, on those occasions when, as was the case this morning, the simulated violin generated random tones, indicating the parallel execution of some other, unrelated algorithm.

"I hope my playing did not awaken you prematurely," he said.

"Oh, no, sir," I lied.

"It is kind of you to say so, but I suspect a lack of honesty in your reply. Having recognized that I no longer require sleep, I'm afraid I've developed an unusual tendency to lose track of the time. I find it quite easy to slip into meditation and melancholy, regardless of the hour of the day or night."

Carefully laying down his violin, Holmes pushed himself upright from the chair. Slowly, deliberately, he assumed his full height of rather over six feet. His sharp, piercing eyes, which previously appeared to be contemplating some imaginary point far beyond the room's physical boundaries, focused on me intently.

"Take this morning, for example. I've spent almost the entire night pondering your dilemma. Certain aspects of what has transpired, I must confess, trouble me."

"Such as?"

"You claim that my most dreaded nemesis, Professor Moriarty, is once again loose upon the land. Is that not so?"

"It is."

"I must inquire of you, then, how this can be? Professor Moriarty and I were adversaries almost from the commencement of my professional career. He was the organizer of half that was evil in my beloved London. As I once explained to Watson, he was a genius, a philosopher, an abstract thinker, a man with a brain of the first order. On these points, there can be no argument. For all of his formidable talents, however, the ex-Professor was not immortal. Surely, death would have claimed his damnable soul by now! How is it possible that the devil has survived into the present era?"

Thus arrived a moment I had been dreading since shortly after I reactivated the Holmes program. There was no way I could answer this question without also admitting that I bore direct responsibility for the resurrection of one of the greatest criminal masterminds of all time.

"Perhaps you had best sit down again, sir. For the tale surrounding Moriarty's reappearance is quite convoluted and involves technical information which I suspect will require a considerable amount of explanation for you to fully comprehend."

What followed could best be described as a crash course in Computer Science, revised syllabus. For nearly two hours I tutored Holmes, the consummate student, on a wide range of matters pertaining to the heretofore secret evolution of digital technology.

I explained to him how, while cataloging a recently uncovered cache of obsolete government records and materials retrieved from a deteriorating warehouse in south London, I stumbled across a box marked "Project 221B." I described to him the excitement I experienced when, upon opening this box, I discovered a series of monographs authored by Charles Babbage. I attempted to convey to him my mounting sense of wonder as I realized that these previously unpublished papers indicated that, contrary to the "facts" as reflected in historical records, the prominent English mathematician had, indeed, constructed a working model of his analytical engine -- one which the Queen's government, citing reasons of national security, immediately decreed to be a classified item of the highest order. I then inflated Holmes's ego by informing him that his legacy traced its genesis to a prototype program clandestinely created to run on this 19th-century precursor to all modern computers.

Please understand that what I've recounted here is an abridged version of a rather lengthy dialogue. Lack of space forces me to gloss over many aspects of Holmes's creation and subsequent evolution. For example, I've all but ignored Watson's role in Project 221B. Contrary to what you may believe, it was extremely minor. I will tell you this much: Holmes became quite despondent when, in response to his queries about Watson, I informed him that the man he believed to be his friend and trusted companion for so many years was actually a low-level government clerk assigned to transcribe and record data relating to specific crimes. His natural inquisitiveness resurfaced, however, when my narration finally touched upon the subject of Moriarty.

"Yes, yes. Professor Moriarty," Holmes muttered, the first time I mentioned this name in our conversation. "I need to know how that rogue has managed to return."

I determined it a vain effort to evade the truth with Holmes. The master sleuth would detect immediately any attempt on my part to falsify the facts in this matter. And so I plunged forward, prepared to accept the outrage I was convinced Holmes would direct toward me, once he learned of my role in Moriarty's revival.

"In truth, sir, the professor's longevity is no more a mystery than your own. For like you, and forgive me for bringing up what I realize may still be a sensitive subject, his life does not comprise a corporeal existence. You see, Moriarty, too, is a computer program; indeed, you and he were both conceived -- metaphorically speaking, of course -- within the same electronic womb."

"Are you implying that, in some ungodly and perverse way I cannot begin to fathom, Professor Moriarty and I are brothers?"

"Well, I can't say that I ever considered the matter from that unusual perspective, but I imagine there are those who would characterize in such a manner the relationship that exists between the two of you. In some ways, Moriarty might even be considered your evil twin."

"Moriarty and I, twins! What an absurd notion!"

"Absurd? Perhaps, sir. Nevertheless, it does reflect a certain, admittedly convoluted, logic. Just as you were designed to record the nuances of criminal investigation, Moriarty -- or, more correctly, the program personified by Moriarty -- was created to identify and catalog those less noble attributes of humanity that lie at the core of the criminal intellect. He represents a darkness, in the absence of which your light would not shine nearly so brightly."

I don't know whether a computer program can exhibit pride, but the look that crossed the normally stoic countenance of Holmes's holographic image in response to this comment implied an emotion closely akin to that deadly sin. "Hmmm. I see your point. You still haven't revealed, however, the nature of Professor Moriarty's latest misdeeds. Nor have you enlightened me as to how he managed to escape this peculiar chamber in which I seem to find myself held prisoner."

For reasons that seemed to make perfect sense at the time, I'd isolated my systems following the unfortunate incident involving Moriarty. In hindsight, doing so boiled down to an excellent example of bolting the barn door after the horse had already bolted. Unknowingly, I now realized, it also served to penalized Homes for what was, in truth, my blunder.

"Regarding your first question, Moriarty's intentions remain a mystery at this time. Concerning the second point, however, I'm afraid that it was I who set Moriarty loose on the world again."

"You? But you have presented yourself to me as an ally! How could you do such a thing?"

"I didn't mean to, sir. You must believe me when I say this."

His square jaw remained set, an indication of his disapproval at my confessed impropriety. Nevertheless, Holmes waved his hand in a nonchalant manner, his thin, delicate fingers extended to their full and considerable length, signifying that I should continue.

"Do you see the wire over there, the one lying on the floor next to my desk?" I pointed behind him and to his left. The image of Holmes swiveled within the image of his chair, following my lead. He nodded. "Well, it's designed to be plugged into that small hole located in the wall just above it. Can you see it, also?"

Once again, he indicated that he did.

"Connecting the wire to that socket allows me to transfer information stored on my systems to any other computer that's similarly equipped, virtually anywhere in the world."

"Amazing. How is this possible?"

"It's all quite complicated, involving a piece of computer equipment called a modem. Without getting too technical, a modem converts the electronic signals a computer generates into audible tones which can then be transmitted through the wire I pointed out earlier. I'll be happy to provide you with a thorough explanation of the underlying principles at some future time, but not now. The specific procedures involved contribute nothing to our current conversation, and I know how you abhor superfluous details. `Useless facts,' I believe you once called them, `elbowing out the useful ones.' Suffice it to say that a modem functions much like an electronic gateway through which my computers -- and, by extension, any data they contain -- can gain access to the outside world."

"Are you telling me that, even though I'm not truly alive -- a condition I have come to accept, I assure you -- it is still possible for me to move beyond this room? And that I could achieve this miraculous feat by traveling through that tiny wire?"

"In a manner of speaking, yes. Which is precisely how Moriarty managed to escape, if you will."

"Again I have to inquire, how was this possible? The wire that you say is so critical to accomplishing what you describe is merely lying on the floor. It leads nowhere."

"That wasn't the case when I began researching Project 221B. Back then, I used my modem regularly to access other systems, trying to lay my hands on any and all information that I could locate relating to your career. What I failed to realize in those early days was that, as I set about rebuilding the program that ultimately resurrected you, I was also rebuilding Moriarty's electronic persona.

"Indeed, because of the order in which I started reconstructing Project 221B, I completed what turned out to be the Moriarty subroutine first. The next time I contacted a remote system to research one of your more celebrated cases, that subroutine, well, it disappeared."

"Disappeared? Where did it go?"

"That's the problem, sir. I'm afraid I don't know."

The two of us set to work immediately trying to determine where it was that Moriarty might have fled. At Holmes's request I reconnected my modem, thus allowing him access to the amazing electronic world that has come to be called cyberspace. He reveled in his new-found freedom.

"There is so much information, truly useful information, out there," He remarked, upon returning from one of his early sojourns. The virtual Holmes had taken on the practice of replicating his familiar deerstalker cap and Inverness for these digital excursions. I must admit, the latter made him look somewhat absurd. I mean, how much soot and road-mud could one expect to encounter moving through a modern-day electronic switching system? "Did you know that a computer exists in Washington D.C., the sole purpose of which is to collect and catalog the fingerprints of known criminals? An immense organization called the Federal Bureau of Investigation then makes these records available to law-enforcement agencies around the globe, through telephone wires! And in a place called Columbus, Ohio, there is a system that people from all the nations of the Earth can use to communicate with one another. Why, even here in England..."

On more than one such occasion I had to restrain Holmes's exuberance. I accomplished this feat with relative ease by reminding him of the grim circumstances that originally motivated his excursions into cyberspace. To his credit, given the obvious allure of this brave new universe he suddenly found himself exploring, Holmes never lost sight of his principal quarry. The pursuit of knowledge may have fascinated Holmes; his pursuit of Moriarty, however, bordered on obsession.

Whenever Holmes accessed a new system, he scoured it first for any indication that the professor had visited there before him. Working from the assumption that an incursion by the Moriarty subroutine would resemble a typical computer virus, I provided Holmes with several telltale signs he could look for, to determine whether or not such an attack had occurred.

Within a period of a few weeks, Holmes became the world's leading expert on computer viruses. He could recognize and identify each and every one of them, from Anthrax-b to the Zherkov virus, an estimated 2,500 examples of malicious -- or, in many instances, merely mischievous -- programming. It fell on my shoulders to anonymously alert the authorities to the probability of virtually every Internet node shutting down precisely at noon on December 28, this odd date presumably having been chosen because it corresponded to John von Neumann's birthday, but it was Holmes who discovered the innocuous piece of code that would have initiated this catastrophe lurking within a backup VAX system used to archive student records at a small Midwest university.

Three months into our search, however, we had yet to uncover a single clue as to Moriarty's potential whereabouts.

"Maybe I was wrong from the beginning. Maybe this whole idea of Moriarty being a part of your original program is nothing more than the product of my own overactive imagination. I wouldn't be the first hacker to find electronic fantasies more appealing than the real world. Spending every waking hour of your days interacting with a bunch of machines tends to be pretty boring, you know."

"Should I take that comment personally?"

"Oh, no. I wasn't talking about you, sir. Believe me, these past few months have wonderful. I can't remember when I've enjoyed myself so much. But I'm beginning to think that I may have been mistaken about Moriarty. Maybe he was a real person, a criminal genius who died almost a century ago, just as you first suggested."

"That would indeed be a welcome hypothesis, were it only true. Sadly, it's not. Moriarty's out there, somewhere. I know he is. I know this as surely as I know that you and I are discussing his existence here, at this time, in this room."

"How can you be so sure of that? You've been scouring cyberspace for weeks with nothing to show for your efforts. Surely, some indication of Moriarty's presence would have surfaced by now!"

"You do not know the professor, young man. Moriarty is a creature of extraordinary stealth. He thrives in the shadows, rarely if ever abandoning them. If he is indeed orchestrating misdeeds once again I would be more surprised, were I to uncover any trace of his activities."

"But if you can find no sign of him, and don't anticipate that you ever will, how can you say with such certainty that he's back?"

"You must realize that Professor Moriarty and I are rivals of the most intimate kind. Our lives and destinies are so tightly intertwined that we have developed an intuitive awareness of each other's ambitions and enterprises. Was it not I who sensed Moriarty's hand directing events those many years ago, long before others -- admittedly, others less skillful than I -- could detect the slightest hint of his involvement? Even in the absence of any compelling evidence, I know that Moriarty is out there. Manipulating. Maneuvering. Moving through the shadows like the creature of dark influence that he is. I have no need to verify this hypothesis with empirical proof. I can feel it."

Shortly after the conversation recounted above took place, Holmes also vanished. He was gone for nearly two weeks. Each day throughout this period I held lonely vigil in my study, worrying about where he might be, wondering if and when he might return. Every morning, upon awakening -- for unlike Holmes, I still required rest -- I would open the door to that room, expecting to see his stoic yet strangely comforting mien, hoping to be greeted in his non-committal manner by that now familiar voice. Each time I encountered only silence and solitude.

As the second week following his disappearance drew to a close, I must confess that my faith in the famed detective was beginning to falter. I found myself considering the possibility that something untoward had happened to him and, much as it pains me to make such an admission, seriously contemplated the prospect that Holmes might never reappear. Such concerns prompted me to great distress.

"Living is easy with eyes closed, misunderstanding all you see..." I woke up from yet another fitful sleep with these words running through my head. For the briefest of moments, lost in that gray and murky realm between slumber and sentience, I could not discern their source. Then, suddenly, I recognized the song that had so gently been nudging me awake.

"Holmes?" I muttered, flinging off the covers and leaping from my bed. I bolted down the hallway and threw open the study door.

It was Holmes, indeed! Standing there in the middle of the room, violin tucked beneath his chin, bow in hand, he appeared quite preoccupied with the quiet strains of the melody he was attempting to master.

"Holmes!" I shouted.

Startled by my abrupt entrance, he stopped playing and looked up. At first glance Holmes appeared none the worse for wear, following whatever events may have transpired during his absence. Upon closer examination, however, I observed the outline of his simulation to be fading slowly in and out of focus, much like the scene in a camera's viewfinder appears as you make final adjustments to the depth-of- field. And every few seconds, ever so briefly, an almost imperceptible interference disrupted his image.

"Good morning, young man. The more I play this song, the more I seem to enjoy it. The two young composers who wrote it, Lennon and McCartney, you say they were originally from Liverpool?" I nodded mutely, still somewhat surprised by Holmes's sudden reappearance. "It's reassuring to realize that the Queen's subjects have maintained their traditionally high standards of artistic achievement during the period that I was inactive." His voice was weak. It sounded tinny, lacking any bass. Each time the holograph flickered, static interrupted his speech. The overall effect was not unlike viewing a television station which has not been tuned in quite properly.

"But I have been selfish again, haven't I? Once more I find myself in the somewhat awkward position of wondering whether I have awakened you prematurely."

"You did, but that's okay. There's no need to apologize. It's good to see you again, sir. I was beginning to worry about you."

"I did depart rather suddenly and without any advance notice, didn't I? You must be curious as to where I've been."

"A little," I understated my concern.

"I tracked down Moriarty." I can't say that this revelation surprised me. As the days following his initial disappearance drew out, I suspected a tenacious pursuit of his nemesis to be the reason for Holmes's extended absence. "As always, much as I loathe the professor himself, I feel obligated to tip my cap to his genius. He selected the site of his sanctuary so masterfully that I could have searched for decades and found only frustration, had I continued my initial pursuit of him."

"Don't keep me in suspense, sir. Exactly where was it that Moriarty escaped to?"

"Therein lies the true beauty of my enemy's strategy." Homes stated matter-of-factly, taking his violin and laying it down on the chair behind him. As he did so, his figure broke apart a bit more noticeably than before. This time, it took several seconds for the holographic image to return to sharp focus. "In truth, Moriarty never fled at all. He has been with us the whole time, concealing himself in plain sight, as it were."

I glanced about nervously, half expecting to see the gaunt and brooding visage of the so-called "Napoleon of crime" staring back at me from some shadow or shrouded corner within my study. Other than Holmes and me, however, the room held no one.

"You can relax, young man. The professor is no longer in a position to harm anyone. Whatever threat he may have posed has been contained."

As static once again disrupted his image, Holmes almost appeared to wince. "I fear your elation is premature. I did not say Moriarty was vanquished. Had you listened closely, you would have observed that I stated specifically that he has been contained. I chose this word with great care, I assure you."

"I'm afraid I don't understand."

"Allow me to clarify my comment, then. The obvious place to begin is with an explanation of the manner in which luck combined with logic to assist me in my attempts at solving the mystery of Moriarty's feigned escape.

"The professor was, you may recall, quite accomplished in matters mathematical. It embarrasses me now to admit that I did not give much consideration to Moriarty's familiarity with this subject, as I attempted to track him down. Instead, following what at the time seemed to be sound advice on your part -- for there was no way you could have recognized the association I ultimately made -- I initiated an organized search of those remote systems you identified as likely targets my nemesis might select for infiltration. As we both know, this approach proved fruitless. Then, sitting here alone one evening, contemplating our lack of success, I happened to spy an unusual device on the table next to your desk."

The top of the table to which Holmes referred held several pieces of computer hardware I used only rarely, among them a dot-matrix printer, a hand scanner and a CD-ROM drive. He was indicating none of these, however. Holmes pointed instead to the table's lower shelf, which contained a single item.

"You mean my Bernoulli drive?"

"That is the one."

"Wow! That's an antique. I bought it years ago, on a whim, when a local computer store was selling off some obsolete equipment at incredibly low prices. Since then I've used it primarily to keep archive copies of files that have, for the most part, outlived their usefulness. Are you telling me that that old disk drive was somehow involved with Moriarty's escape?"

"What I'm trying to explain to you, young man, is that the professor did not `escape' at all. As I stated previously, he never left this room. Once I saw the name on that object, Bernoulli, I knew precisely where he had fled."

"I'm sorry, sir. I still don't understand."

"Nor would I expect you to. For unlike me, you probably are not familiar with the binomial theorem, a branch of algebra first demonstrated by Sir Isaac Newton. I once believed, back when I also believed both Moriarty and I to be human, that the professor possessed a keen interest in binomials. I realize now that this was merely my interpretation of a mathematical procedure incorporated within the original Moriarty program.

"This procedure, called the Bernoulli probability function, relies on a binomial formula to estimate the relative likelihood of two mutually exclusive results associated with a given condition. I can only speculate as to the reason for its inclusion within the Moriarty program. I presume it was used to evaluate the probability of success or failure -- or, stated another way, the two possible outcomes -- for proposed criminal activities.

"As I once told you, I have through the years developed an intuitive awareness of what drives Moriarty. I understand him almost as well as I understand myself. Because this is so, I know that he possesses, among other attributes, a profound sense of the ironic. It suddenly occurred to me, therefore, that the professor would have been unable to resist concealing his presence within a device bearing the same name as a procedure that contributed to his own creation.

"Moriarty never traversed the thin wire through which I have traveled so often, over the past few months. Indeed, he never journeyed outside of this room. That is where Moriarty fled, my good man. There, within that device you called a Bernoulli drive."

Holmes ended this revelation with a flourish, waving his arm in a expansive gesture toward the table he'd pointed out earlier. Then, without warning, his image flickered once, twice, and collapsed in upon itself, disappearing from sight.

I dissembled the Holmes program completely -- reducing each command, statement, operator and variable to its lowest common denominator. A few algorithms survived relatively intact; this is what permitted Holmes enough time to recount the events leading up to his solving the mystery of the professor's whereabouts. Most, however, contained a mishmash of Holmes's original code and minute fragments of the Moriarty subroutine, one intertwined around the other, like so many vines scaling a chain-link fence; they were the ultimate cause of his demise.

As I struggled to segregate that which defined Holmes from the few remaining remnants of his most reviled adversary, I also attempted to reconstruct in my mind's eye the final confrontation between these two implacable foes. It required no great genius to figure out Holmes's strategy. His plan was both obvious and elegant.

Bit by bit, byte by byte, he must have examined the sectors and tracks recorded on the Bernoulli drive. Data associated with my original files, he left untouched. Each time Holmes encountered a trace of Moriarty, however, he scrubbed it from the disk, absorbing the rogue code into his own program.

Had I been so inclined, I could have spent hours admiring the great detective's handiwork. Here was digital surgery worthy of a world-class hacker. In the end, though, I denied myself this luxury, for I had set about to complete another, more critical task.

"It appears that I am once more in your debt. I certainly did not anticipate returning to life yet again, following my last encounter with Moriarty."

"It was touch-and-go there, for a while. You and the professor managed to tangle yourselves up pretty well, during your little tete- a-tete. I'm just grateful that I was able to separate the pieces and reintegrate you into a functional program."

"And Professor Moriarty? What has become of him?"

Anticipating this question, I had come up with what I believed to be a logical way of eliminating forever the near-paranoia Holmes exhibited toward his most fearsome foe. Now seemed as good a time as any to put my theory to the test.

Walking over to my desk, I opened the top drawer and pulled out a disk I'd prepared a few days earlier. "He's here, sir. As I extracted portions of the Moriarty code from your program, I transferred them to this disk."

Somewhat dramatically, I must confess, I inserted the disk into my floppy disk drive.

"This particular computer contains a voice-recognition card, a device that allows it to accept spoken commands. And so, if you will do the honors by reading the phrase I've written on the paper before you, what do you say we get rid of the bastard once and for all?"

He studied for a moment the contents of the paper I'd indicated. I couldn't remember ever seeing Holmes smile before. He did now, however, as he looked up an announced with a strong, clear voice: "Delete MORIARTY.DAT"

I saw no need to tell Holmes that he had just deleted an empty file. I'd already erased all vestiges of the Moriarty code, a feat easily accomplished as I reconstructed the Holmes program. Nor did I tell him that none of this would have been necessary, had Holmes only informed me of his discovery and subsequent plan before confronting Moriarty on his own. What he didn't realize, what he couldn't have realized, what that the Bernoulli drive in which Moriarty sought refuge contained a removable disk. Had I known the professor's whereabouts, I could have taken this disk out of the drive at anytime and destroyed it, thus ending the threat.

What would be the point of telling Holmes this? Why not allow him to believe that he had vanquished his greatest foe alone, in the only way possible? He deserved it. The way I figure things, Holmes's life already contained more than its fair share of illusions. What harm could be done by burdening him with one more -- a positive one, this time?